Object detection techniques are used to locate, identify, or verify one or more specific objects in images. For example, automatic face detection has a variety of useful applications in security systems, face tracking systems, photo editing systems, and so on. Although various efforts have been undertaken, face detection remains to be a challenging task because of the variances in images of face pose, facial expression, background, view, illumination, and skin color. Such variations cause the face data distribution to be highly nonlinear and complex. Moreover, in applications such as real life face detection, the camera limitations and pose variations make the distribution of faces in feature space dispersed and complicated. As a result, the robustness of conventional face detection is now relatively low. Detection of other objects suffer from similar deficiencies.